1. **State the problem:** We are given two similar triangles, Triangle A with sides 8, 10, 10 and Triangle B with sides 12, 15, 15. We need to find the scale factor from Triangle A to Triangle B in fraction form. 2. **Recall the formula for scale factor:** The scale factor between two similar triangles is the ratio of any pair of corresponding sides. Since the triangles are similar, all corresponding side ratios are equal. 3. **Calculate the scale factor:** Choose corresponding sides 8 (Triangle A) and 12 (Triangle B). The scale factor $k$ is $$k = \frac{\text{side in Triangle B}}{\text{corresponding side in Triangle A}} = \frac{12}{8}$$ 4. **Simplify the fraction:** $$k = \frac{\cancel{12}^{3 \times 4}}{\cancel{8}^{2 \times 4}} = \frac{3}{2}$$ 5. **Interpretation:** The scale factor from Triangle A to Triangle B is $\frac{3}{2}$, meaning each side of Triangle B is $\frac{3}{2}$ times the length of the corresponding side in Triangle A. **Final answer:** $\boxed{\frac{3}{2}}$